Cut the breasts in half lengthwise and set them aside.
In a large bowl, whisk together the pickle juice, milk, powdered sugar, garlic powder, onion powder, pepper, salt, and paprika. Add the chicken pieces to the marinade and coat the chicken completely with the marinade. Cover the bowl with plastic wrap and place it in the fridge for at least 30 minutes, up to 4 hours.
If needed, prepare the Honey Roasted BBQ Sauce and then cover it with plastic wrap and place it in the fridge until ready to use.
Preheat the grill over medium heat. Cook the chicken, occasionally flipping until an internal temperature reaches 165°F in the thickest part of the breast, for up to 15 minutes total. Remove the chicken from the heat and top each piece of chicken with a slice of cheese to melt slightly.
To assemble the sandwiches, remove the tops of the buns and add lettuce and a tomato slice to the bottom bun. Then add a piece of chicken followed by a slice of bacon broken in half, so it fits the sandwich.
Spread the honey-roasted bbq sauce on the cut side of the top bun. Add the top bun to the assembled sandwiches.
Serve immediately.
Notes
This is a very close copycat to the original. You can leave off the cheese and bacon if you prefer, and this would make their classic grilled chicken sandwich.
They always serve honey-roasted bbq sauce with grilled chicken sandwiches, and to me is the best part of the whole thing! It is by far my favorite sauce that Chick-Fil-A offers, and my copycat recipe is very close to the original as well.
Chick-fil-A offers pepper jack cheese or Colby Jack cheese to top the sandwich. You can use whatever cheese you want, but it would no longer be a copycat recipe.
Store any leftovers in the fridge for up to 3 days unassembled and separately. Warm the chicken in the microwave or oven until just heated through, or it may become dry. You can also use it cold for a cold version of the sandwich, which is amazing as well.
You can also freeze any leftover chicken in a freezer-safe airtight container for up to 3 months.